Description of Disk Investigator program from developer(s):

Disk Investigator helps you to discover all that is hidden on your computer hard disk. It can also help you to recover lost data. Display the true drive contents by bypassing the operating system and directly reading the raw drive sectors. View and search raw directories, files, clusters, and system sectors. Undelete previously deleted files. Verify the effectiveness of file and disk wiping programs.

Disk Investigator is a Freeware program.
You can download and
use it absolutely free.